Process of treating or forming an insoluble plutonium precipitate in the presence of an organic surface active agent



July 18, 1961 J. H. BALTHls 2,992,888

PROCESS OF TREATING OR FORMING AN INSOLUBLE PLUTONIUM PRECIPITATE IN THEPRESENCE OF AN ORGANIC SURFACE ACTIVE AGENT Filed Dec. 29, 1944Cofo/-med l W rz. ...3,

[ofc/"med 20% Ares/dene l l l I l l 02468/0/2/4/6/6202 77M;- OFQU/fscf/VCE BEFORE CONT/20u50 Cf/v TQM-06,4 770A/ /N M/A/urEs IN VENTOR.

2,992,888 Patented July 18, 1961 PRocEss F TREATING on FORMING AN 1N-SOLUBLE PLUTONIUM PRECIPITATE 1N THE PRESENCE OF AN ORGANIC SURFACEACTIVE AGENT Joseph H. Balthis, Wilmington, Del., assignor to the UnitedStates of America as represented by the United States Atomic EnergyCommission Filed Dec. 29, 1944, Ser. No. 570,419 4 Claims. (Cl.23--14.5)

This invention relates to a procedure for processing of materialscontaining the element of atomic number 94, known as plutonium, -forseparating the plutonium from extraneous matter such as substances ofthe kind present in neutron irradiated uranium exemplified by uraniumand especially fission products, and the like radioactive contaminants.More particularly, this invention concerns a separatory andconcentration procedure involving the use of a iluoride type of carrierwherein certain improved procedure is employed in forming the carrier.

As described herein, the isotope of element 94 having a mass of 239 isreferred to as 94239 and is also called plutonium, symbol Pu. Inaddition, the isotope of element 93 having a mass of 239 is referred toas 93239 Reference herein to any off the elements is to be understood asdenoting the element generically, whether in its liree state or in theform of la compound, unless indicated otherwise by the context.

Elements 93 and 94 may be obtained 1from uranium by various processeswhich do not form a part of the present invention including irradiationof uranium with neutrons from any suitable neutron source, butpreferably the neutrons used are obtained from a chain reaction ofneutrons with uranium.

Naturally occurring uranium contains a major portion of 92U238, a minorportion of 92U235, and small amounts of other substances such as UX1 andUX2. When a mass of such uranium. is subjected to neutron irradiation,particularly with neutrons of resonance or thermal energies, 92U238 bycapture of a neutron becomes 92U239 'which has a half life of about 23minutes and by beta decay becomes 93239. The 93239 has a half life ofabout 2.3 days and by beta decay becomesv 94239. Thu-s, neutronirradiated uranium contains both 93239 and 94239 but by storing suchirradiated uranium for a suitable period of time, the 93239 is convertedalmost entirely to 94239.

In addition to the above-mentioned reaction, the reaction of neutronswith iiss-ionable nuclei such as the nucleus of U235 results in theproduction of a large number of radioactive fission products. As it isundesirable to produce a large concentration of these tission productswhich must, in view or their rad-ioactivity, be separated from the 94239and further as the Weight of radioactive ssion products present inneutron irradiated uranium is proportional to the amounts of 93239 and94239 for-med therein, it is preferable to `discontinue the irradiationof the uranium by neutrons when the combined amount of 93239 is equal toapproximately 0.02 percent by weight of the uranium mass. At thisconcentration of these substances, the concentration of ssion elementswhich must be removed is approximately the same percentage.

A number of process have already been proposed for accomplishing theseparation and concentration of Pu. Certain of these processes aregenerically known as the bismuth phosphate type process and the wetuoride type of process. These processes are the invention of others andthe detailsof the processes are described in copending applications asfor example application Ser.

No. 519,714, now U.S. Patent No. 2,785,951, issued March 3, 1957, to bereferred to hereinafter, which gives details relative to such processes.Consequently, all of the details of operation of the aforementioned[processes are not described herein.

In some instances, it has been customary to utilize in the sameseparation and recovery process both the bismuth phosphate treatment andlanthanum uoride treatment. The present invention in its preferredembodiment concerns the formation of the uoride type of precipitatesexemplified by a lanthanum lfluoride precipitate carrying Pu. Inprocesses of the aforementioned type, either combination processes Whereseveral dilerent types of carriers are used, including the formation ofa uoride precipitate, or processes Where fluoride compounds are more orless directly precipitated, the formation of these fluoride compoundscarrying Pu or iission products or comprising a fluoride compound of Pumay present certain diiculties. For example, one carrier precipitatecommonly formed is lanthanum fluoride. This precipitate has been formedunder acid conditions by adding to the acid solution a source offluoride ions and a source of lanthanum ions. The characteristics of theprecipitates formed are such as to present some diiculty of separationbecause of the finely divided nature and `dispersion thereof. That is,it has been required to centrifuge these precipitates at relatively hghspeeds for extended periods or to employ a special filtration techniquedior separation from the surrounding liquid. It has also been requiredto precipitate the LaF3 in two portions, separating after eachprecipitation.

In accordance with the present invent-ion, it has been found that aprecipitate of better characteristics may be formed by the use ofsurface active agents either alone or in conjunction with certain othermodifications of precipitation conditions.

The meaning of the terms bismuth phosphate type of process, fluoridetype of process, product and byproduct precipitate, coformed, preformed,and similar terms will be apparent as the description proceeds.

The invention has for 'one object, to provide improvements in methodsfor the separation and recovery of plutonium.

Another object is to provide a method of separating plutonium byprocedure wherein certain additions different from those heretofore usedare employed.

Another object is to provide improved procedures for forming certainprecipitates.

Still another object is to provide a new procedure patn'cularly usefulin forming a uoride carrier precipitate containing Pu.

Another object is to provide a new procedure for forming by-productfluoride carrier precipitates.

Still another object is to provide a procedure for forming fluoridecarrier precipitates which exhibit improved characteristics.

Another and particularly important object is to improve the centrifugingcharacteristics of lanthanum fluoride precipitates.

Still Ianother object is to provide a type of process which lends itselfto combination with steps already known or practiced.

Another object is to provide a type of process which may employ thematerials used in existing processes, but under Vdifferent conditions,and which may be carried out in existing equipment Without change, orwith a @t equipment change.

Stili another object is to provide treatments for uoride precipitateswhich 4do not exert a detrimental effect on subsequent process steps towhich the precipitates may usually be subjected.

Other objects will appear hereinafter.

I have found that Pu in admixture with various extraneous material maybe separated and concentrated byY the use of the series of stepsinvolving the formation of certain carrier precipitates. Thesetreatments may be generally similar to known practice as respectsreagents, temperatures and similar features. However, I have found thatthe formation of such carrier precipitates may be rendered simpler andmore eilicient by rnodication of precipitation conditions, the use ofsurface active agents and other features as will be described in detailhereinafter. By the formation of the carrier precipitate under theconditions of the present invention, not only are the advantagespreviously obtained in the processes still obtainable, but there areIalso obtained advantages such as the production of precipitates havingimproved centrifuging characteristics.

Illustrations of some of the types of carrier precipitates which may beimproved by the present invention are described in application Ser. No.519,714, filed January 26, 1944, Thompson and Seaborg, and reference ismade to that application for further disclosure, details thereof beingomitted from the present disclosure except Where necessary to anunderstanding of the present invention. As set forth in saidapplication, it has been discovered that plutonium has more than -oneoxidation state, including a lower oxidation state or states referred toherein as Pu@ in which the element is characterized by forming insolublephosphates and fluorides and a higher oxidation state or states referredto as Pu@ in which the element forms soluble phosphates and fluorides.

In accordance with the present invention, for example, a fluoride typecarrier precipitate such as a LaF3 precipitate as described in theaforementioned application would be formed by procedure involving theuse of a surface active agent such as Aresklene or the like.

The solutions containing Pu which may be treated, and in which thefluoride precipitate may be formed by myinvention `are the same type ofsolutions as heretofore treated. A common type of solution containing Pusubject to separation and recovery procedures is a solution which hasbeen initially processed by the bismuth phosphate type tof treatment.Such type of solution and its treatment are described in detail inapplication Ser. No. 519,714 aforementioned. These solutions comprise anitric acid containing liquid having a content of Pu therein. The nitricacid solution may also contain other acids such as a content ofphosphoric acid and oxalic acid. The solution may also contain cert-ainextraneous matter such as radioactive materials wh-ich the subsequentlyapplied uoride precipitation treatments may eliminate or reduce. Asindicated above, by means of a fluoride precipitation treatment appliedto the solution containing the Pu inthe reduced (r) condition, theresultant iiuoride precipitate (product precipitate) carries the Pu awayfrom extraneous matter. By means of a fluoride precipitation applied tothe solution having the Pu in the oxidized (o) state (by-productprecipitate), extraneous matter is carried away by the fluorideprecipitate leaving the Pu@ in the supernatant liquid from thisprecipitation.

'Ihe formation of fluoride precipitates exemplied by lanthanum fluoridecarrier precipitates may be accomplished in several different Ways. Apreformed precipitate is produced by incorporating a source of an excessof fluoride ions such as excess hydrogen fluoride into the solutioncontaining Pu in which the carrier precipitate is to be formed.Thereafter a source of lanthanum ions is added to the process solution.In other words, a prieformed precipitate is produced by proceduredescribed as a lanthanum strike.

A coformed precipitate is produced by oper-ation described as a hydrogenfluoride strike. That is, the source of lanthanum ions is rstincorporated in the solution in which the carrier is to 4be formed,thereafter the hydrogen fluoride is added to cause the formation of thelanthanum fluoride precipitate.

Broadly, therefore, my invention may be applied to various typesolutions in which the precipitates may be formed in various ways. Thesolutions to be processed by my invention preferably have -added theretoone or more surface active agents as may be required at substantiallyany time during the process dependent upon the particular compositionand condition of the solution and the nature of the agent added.

For a further understanding of my invention and appreciation of some ofthe advantages of the invention in improving the characteristics of theprecipitates obtainable, by the incorporation of surface active agents,a number of examples are set forth hereinafter. In general, for thepurposes of comparison some runs are described in connection with theexamples as carried out for the purposes of control. That is, some ofthe runs were carried out under various conditions as will be discussedbut without the use of surface active agents in the process. It will benotedV that some improvement in the precipitate characteristics may beobtained by the control of certain conditions as will be discussed. Thenexamples were carried out in a manner substantially exactly the same asthe particular control run -but with the addition of surface activeagents in accordance with the present invention.

In order to make a more denite comparison, tests were made on slurriesfor determining the rate of settling and sedimentation volume. This wasdetermined by pouring s-lurry (carrier precipitate plus surroundingliquid) into graduated cc. tapered glass tubes and recording the volumeof sediment as a function of the time. By comparative tests with thecontrols and the runs comprising surface active agents an indication ofthe improvement obtainable `by employing a particular feature of theinvention is given.

Another measurement which may be made is referred to herein as thecentrifugation improvement factor. This is the ratio of centrifugableproduct in the supernatent from untreated precipitate (control) to thatin the supernatant Afrom treated precipitates (precipitates in whichagents in accordance with the presen-t invention have beenincorporated). The slurries under such comparison are centrifugedsubstantially identically.

iIn further detail, this may be accomplished by pipetting, for example,one cc. samples from each of the mechanically stirred slurries to becompared, transferring to 3 cc. :glass tubes constricted at the bottomto retain solids while pouring off the lbulk of the supernatant. Thesesamples are simultaneously centrifuged in these tubes under carefullycontrolled conditions (for example one minute at 220 G) followed byimmediately pouring olf the supernatants into 50 cc. containers. Theproduct content of the supernatants may be determined by measuring theiralpha activity.

The term relative centrifugal force (RCF) as used herein isconventionaland refers to the maximum obtained. In the runs describedthe time indicated for centrifugation includes that required to reachthe desired r.p.m. 'but does not 4include the time of coasting to astop. .As will be observed as the description proceeds, in large scalecontinuous centrifuges a relative centrifugal force of greater than 1500G is usually applied in order to cause satisfactory separation of theuoride carrier precipitate. On the other hand, when iluorideprecipitates are `formed employing procedure in accordance with thepresent invention, a force of even below 500 G is in many instancesample to obtain satisfactory centrifugation.

An additional understanding of this aspect that prior procedure :hasrequired thigh speed centrifuging may be had by reference to thefollowing table of data covering continuous centrifugation operations:

In producing the iiuoride precipitates described as centrifuged in thepreceding table, oxalic acid reduced solution was made of the normalityin HF indicated. There -was then added a quantity of lanthanum ammoniumnitrate solution to give a concentration equivalent to about 125milligrams of Lai'3 per liter. This was added at about 3% per minute.The slurries (lanthanum uoride precipitates plus supernatant liquor)were digested at between 25 C. and 32 C. and then subjected tocentrifuging. As may be observed from the table, when centrifuge speedsof greater than 1700 r.p.m. were employed, only about 11i/2% of the Puwas retained in the precipitate remaining unseparated. When thecentrifuge speed was reduced to about one-half, namely, when an r.p.m.of about 870 was used the loss increased to about 15%.

It is therefore apparent from the foregoing that fluoride precipitateswhen prepared in a conventional manner have required relatively highcentrifuging speeds to obtain reasonably satisfactory separation.

It has been found that the centrifuging characteristics of suchlanthanum fluoride precipitates may be improved somewhat by subjectingthem to vigorous agitation during formation. In general under normalconditions lanthanum uoride precipitate remains partially suspended inaqueous medium for one-half to three hours when agitation isinterrupted. When the precipitate has been preformed, the almosttransparent precipitate ilocculates after several minutes and settles toa relatively large volume of gelatinous sediment. VCoformed lanthanumfluoride is more opaque and settles more slowly to a smaller volume ofless occulent sediment.

As indicated, it has been found that the degree of agitation during theformation of such precipitates affects the centrifuging characteristicsof both preformed and coformed lanthanum iiuoride. 'Ihe ease ofcentrifugation for the precipitates obtained increases with'the rate ofagitation employed during their process of formation. In carrying outthese runs Where agitation was applied, identical paddle agitators wereused. The preferred agitation under the particular circumstancesinvolved the use of a bafed tank with the agitator revolving at 220r.p.h. However, other rates of agitation may be used.

Both the preformed and coformed lanthanum fluoride precipitates wereprepared by using 125 milligrams -per liter ofLa+3 and 0.5 N HF. Theprecipitates were Ydigested for one hour. The solutions treated and inwhich the precipitates were formed werestandard oxalic acid reducedsolutions The effect of the agitation in improving centrifugability isindicated in the next table.

PERCENT OF ORIGINAL Pu IN SUPERNATAN'T AFTER I have found that, ingeneral, by adding surface active agents in processes of formingprecipitates of the class described, the characteristics of theresultant precipitates may thereby be substantially improved. Thesettling rates of such precipitates and other characteristics areimproved yet at the same time the ability of the precipitates to carryPu in the event the Pu is in a reduced condition, or to carryby-p-roducts in the event oxidizing conditions are present, is notimpaired. That is, a precipitate of the class described prepared by thebest procedure available including such modifications as employing rapidagitation during formation of the precipitate, may be further improvedbythe utilization of surface active agents in accordance with thepresent invention.

The agents which may be used may be cationactive, anionactive, ornon-ionic. As is known, there are an extremely large number of suchagents available commercially. In the practice of the present inventionit is possible to use commercially obtainable agents. Consequently, forconvenience and practicability of description, reference will be madeherein to the commercial name under which some of these agents areknown. No attempt is made herein to enumerate all possible agents.Likewise, the invention is not to be regarded as limited as respects anagent manufactured by some particular method.

One agent which has been found to be quite satisfacf tory is Aresklene400. This material is commercially obtainable and is stated to be adibutyl-phenyl-phenol sodium disulfonate. Another agent which has beenfound to be quite useful is Neomerpin N. Likewise, this is acommercially obtainable compound stated to be an alkyl naphthalenesulfonic acid.

Many other surface active agents are described in Industrial andEngineering Chemistry, Industrial edition, for January 1941, and in anumber of other publications. Still another agent which has been foundto give good results when used in the present invention in lecithin. Thecommonly available commercial products are obf tained from soy beans andcontain soya oil, free fatty acids and phosphatides. Soya lecithin isavailable in several different grades. For example Lipoidol is a loWcost technical grade. Yelkin C is a commercial product stated to be aWater dispersable grade of soya lecithin containing Carbitol (diethyleneglycol monoethyl ether).

For the purposes of illustrating some of the specific embodiments of myinvention, reference is made to the following examples.

ExampleI In this example the species of agent added was soya lecithin.Under this example a number of runs were carried out as will bedescribed wherein the agent Was present during and after the formationof the precipitate. Also in the various different runs, differentquantities of agent were added.

Run (a) was a control run. The starting solution was standard oxalicacid reduced nitric acid solution of the ltype already described. Thesolution contained Pu and had been subjected to prior bismuth phosphatetreatment. The solution was in a condition to be subjected to alanthanum iiuoride carrier precipitation treatment for carrying down thePu.

A ml. sample of this solution was used for the control. The lanthanumfluoride carrier precipitate was formed therein by an HF strike. Thatis, approximately 10.4 ml. of a source of lanthanum ions (La+3) wereincorporated into the solution. This source contained 2.5 mg. of Lat3per ml. Thereafter there was added 4.1 ml. of concentrated HFincorporated at the rate of 3% per minute. The resultant precipitate wasdigested for 11/2 hours at room temperature. The slurry was poured intoa l0() ml. tapered glasstube of the type already described undersettling and sedimentation tests and permitted to settle, The observedsettling as a function of "3 time, was noted and the data plotted aswill be referred to in connection with FIG. 1 of the attached drawingforming a part -of vthe present application.

Run :(b) Vwas carried out substantially vthe same -as the preceding runexcepting that there was present during the precipitate formation acontent of soya lecithin. The amount added was approximately 22% weightbased on the weight of lanthanum. Likewise in this run after digestionof the precipitate the slurry was poured into a 100 cc. bottle and thesettling observed, the data being recorded as illustrated in FIG. 1.

Run (c) was carried out substantially identical with the preceding runsexcepting that in this run the quantity of soya lecithin agentincorporated was 50%. This was incorporated before precipitation, andconsequently was present during the precipitate formation. The settlingdata with respect to this run was recorded as indicated in FIG. l.

Run (d) was likewise similar to the preceding methods excepting that 22%soya lecithin was added after the lanthanum uoride precipitate hadformed. In other words, the primary difference in this run over run (b)was merely the point or time of addition in the process, namely afterthe lanthanum fluoride precipitate had formed. The settling rate wasobserved and the data recorded as illustration in FIG. l.

Run (e) likewise Vwas generally similar to the preceding runs excepting`that in this run 40% lecithin was added .after "the precipitate hadformed. The settling rate was noted and recorded as illustrated in FIG.l.

Referring now to FIG. 1 of the drawing, by reference to the control andcomparison of `this curve with the other curves, it will be observedthat the addition of the agent either before or after vprecipitateformation im proves the settling rate. It may be further noted that inthe case of the particular agent under description, and the otherconditions of the runs, that the addition of the agent after theprecipitate formation gave a greater irnprovement in the settling rate.While this is significant with respect to the lparticular exampledescribed, it is desired 4to point out that in the instance of someagents, the greatest improvement may be obtained by having the agentpresent during the precipitate formation. In general, however, in allinstances whether the agents be added before, during, or afterprecipitation, improvement may be obtained. Hence, it is not desired tolimit the present invention as respects the exact time and point ofagent addition.

Example :Il

In this example `the species of agent added to improve the fluoridecarrier precipitate was agar-agar. This is a well known and vreadilyavailable material, consequently, further description thereof is notrequired. Likewise, in this example a number `of runs were carried outwherein various amounts of the agar were incorporated under avariety-of' conditions. However, for the purposes of this example itappears satisfactory to describe merely a few of these runs illustrativeof the action thereof.

`Run (f) constituted the .control.run. 100 ml. of starting solution-wasemployed for the control. This starting solution comprised an oxalicLacid reduced nitric acid solution containing Pu which had been freed ofat least a part of its contamination by preliminary treatments. Therewas incorporated in-to the solution approximately ml. of solutioncontaining 2.5 mg. of La+3 per ml. Thereafter there was incorporated 0.8ml. of concentrated HF added at the rate of 3% per minute. The resultantslurry was digested in a conventional manner and .poured into acontainer for observing `the settling in the manner comparable to thatalready described. The settling `of the control was observed and Vthe.data plotted as illustrated in FIG. 2.

Run (g) was exactly similar to the preceding runex- 1cepting that thesolution was madeapproximately11%fin agar before forming theprecipitate. That is, approximately 1.25 ml. of a 0.02 percent agarsolution was added so that the agar wouldV be present during theformation of the lanthanum fluoride precipitate. After digesting 'in amanner comparable to the control, the slurry was poured into thegraduated container for observing the settling rate. The data concerningthis run is recorded in FIG. 2.

Run (h) was similar to the preceding examples excepting that thesolution was made 10% in agar prior to precipitation. That is,approximately 12.5 ml. of the agar solution was incorporated. Afterprecipitate formation and digestion, theslurry was poured into acontainer for observing the settling. The data on this run is recordedin FIG. 2.

A number of other runs were carried out wherein other concentrations ofagar were tried. Since the data observed is to a large extent merelycumulative, inclusion herein is considered unnecessary.

Referring to FIG. 2, it will be noted that the incorporation of even the1% agar improved the settling. The incorporation of the 10% of an agentstill further increased the settling rate. The agar addition caused therapid settling of the precipitate into a slimy oc somewhat on thevoluminous side. The supernatants from the processes in which agar wasused were not as clear as supernatants from operations where otheragents were used. For example, as will be described. Aresklene not onlygives rapid settling, but the resultant supernatant very quickly becomescompletely clear.

Example Ill -In this species the agent used was Aresklene. Likewiseunder this example a number of runs were carried out for vpreparingiboth preformed and coformed precipitates. In addition the variation wasmade in the process of..permitting the slurries to undergo a period ofquiescence prior to centrifuging. lIn all of the runs described in thisexample, the lanthanum fluoride precipita-te was formed by using .aconcentration of La+3 of 125 mg. per liter. The concentration ofhydrogen fluoride was 0.5 N. The type of solution treated was oxalicacid reduced nitric acid solution containing Pu of the type as alreadydescribed.

yCertain data noted in respect to the several runs, is set forth inthetable which follows, .relative to the `percent of `product insupernatant after one minute of centrifugation at 220 G.

Y control.

It will be observed from the data set forth in the table .thatathepercentage of `product remaining in the supernatant in the runs wherethe agent hadbeenincluded was much smaller than in the control runs.This signifies that the addition of the agents permitted thecentrifuging out `of a much larger quantity of product in the oneminutecentrifugation at 220 G. Asindicated, a number of runs were conductedandthe results averaged, this information being recorded as illustratedin FIG. 3. Y It will be observedthat under the same circumstances thecentrifugation loss when ani-.agent is present may be considerably lessthan half as maybe noted by comparison with the QA large number of otherexamples have been carriedout along the same general lines as have been`described in detail above. In these examples various vagents have beenincorporated at various stages in the process of forming both preformedand coformcd precipitates. Likewise the liquids treated were of usualtypes. For convenience of consideration, the infomation respecting thesefurther examples is summarized below in the following table IMPROVEMENTIN OENTRIFUGABILITY AOHIEVED BY SURFACE ACTIVE AGENTS AGENTS ADDEDBEFORE PRECIPITATION OF Lara Centrimg./1. HF ugation Example Type ofFlocculating agent of norim- No. precipitate La mality provement factorIV Coformed-.- 20% Aresklene 125 0. 5 8.0 V- do 20% Neomerpin N-. 1250.5 4.0 VI do 50% Fixanol 125 0. 5 1. 0 VII- Preformed. 20% Aresklene125 0. 5 1. 6 VIII... do 20% Neomerpln N-- 125 0. 5 2. 4

AGENTS ADDED AFTER PRECIPITATION AND ONE HOUR DIGESTION F LaFg IXCoformed.-- 20% Aresklene 125 1. 0 4. 3 d 20% Yelkin C 125 1.0 3.0 20%Aresklene 125 0. 5 4.3

20% Yelkin C 125 0. 5 3. 2

20% Neomerpin N 125 0.5 5. 0

20% Aresklene 125 1. 0 2. 2 d0 125 0. 5 1.2

As indicated above, the operation of the invention is not limited to aspecific type agent. Satisfactory results have been obtained withanion-active, cation-active, and non-ionic agents. Informationillustrating these different groups is set forth in the table set forthbelow. All of the agents added produced substantially improved results.

Agent present during Agent added after LaF3 LaF3 precipitation(testprecipitation (testing ing method: Add agent method: Coform LaFa inClassification tosolution,coform LaFg 0.2 N HF, add agent, of agents in0.2 N HF, compare compare rate of settling rate of settling and sediandsediment volume to ment volume to that of that of untreated control) anuntreated control) Aresklene 40G-rapidly Neomerpin N.

settling tlocs. Agar-rapid settling of Aresklene 400. Amon-active.-llocs occupying a large volume. Duponol G-larger sedi- Duponol G.

ment volume.

Duponol ME. Agar. Fixanol-rapld settling at high concentration of(lation-active- Slln'ine Kw rapd Soya lecithin (Yelkln C).

settling at high concentration of agent. Nonionic Tergitol Penetrant 04-some coagulation.

Example XX In this example soya lecithin lwas added -in a mannen thesame as described, in three runs, using a centrifuge having a 12 bowl,to flocculate the LaFS-product precipitate produced by precipitation in0.2 N HF. Twoy of the treated precipitates (slurries) were centrifugedat 410 G, the other at 1510 G. Product losses in the centrifugeefliuents were normal (1.9%, 1.3%, and 0.6%). It is apparent from theforegoing that by the use of the present invention it was possible torun the centrifuge at about one-third of the usual speed and obtain aseparation substantially as good and in some instances better than inprior conventional operations. The separated precipitate was thensolubilized by metathesizing to lanthanum-plutonium hydroxides bytreatment with aqueous KOH. Metathesis waste losses -were normal. Anitric acid solu- 10 tion of the metathesized product behavedsatisfactorily in a concentration cycle thereafter carried out.

Example XXI An aqueous nitric acid solution containing oxidizedplutonium and radioactive fission products was provided with suicientbismuth in the form of nitrate to yield in the final mixture a bismuthconcentration of 21/2 grams per liter. Sufficient phosphoric acidsolution was Iadded to provide a `0.1 molar HgPO.,l solution uponprecipitation of the bismuth as bismuth phosphate. The mixture wasdigested for one `hour at 75 C., then an amount of Neomerpin N equal to20% by weight of the bismuth present was added and the mixture wasdigested for an additional half houJ.` during which the solution cooledto room temperature. 'Ihe mixture was then centrifuged to separate thebismuth phosphate precipitate and radioactive fission products. Afterthe separation, the solution contained less than one-half as muchresidual fission products as contained in similar solutio-n formed in acontrol test ornitting the surface active agent but carried out underotherwise similar conditions.

Example XXII A solution containing oxidized plutonium and radioactivefission products was treated with suflicient hydrogen iiuoride solutionto provide a final concentration of 0.2 N HF after precipitation.Sufficient lanthanum was -added as a 1% HNO3 solution of lenthanumammonium nitrate to provide mg. of lanthanum per liter of solution. Themixture was digested at room temperature for 1/2 hour with agitation.20% by weight of Aresklene, based on the weight of lanthanum present,was then added and the mixture was digested for one hour more at roomtemperature. It was then centrifuged to separate solid matter. IIhecentrifuging time for removing 4the precipitate was approximatelyone-fourth the time required for a corresponding separation in a controltest under similar conditions but omitting the surface active agent.

The use of an -kyl-aryl alkali metal sulfonate, exempliiied byAresklene, is preferred. However, various other agents also givematerially improved results such as the use of Neomerpin N and soya.lecithin. In general, under average conditions around 15-30% by weightof the agent based on the weight of lanthanum is a satisfactory quantityto use either singularly or in the aggregate in the event more than onelagent is used. However, amounts from 1% to 200% have been tested andfound to give improved results. In processes of the present type Whereit is desired to obtain concentration, and it is desired to keepquantities to a minimum, the use of excess is preferably avoided but isnot precluded. The use of large excesses might carry over intosucceeding steps and require added steps for effecting their removal. Insome instances, the improvement obtainable by the use of agents in`accordance with the present invention may be taken advantage of topermit reduction in the number of precipitations and centrifugationsrequired for satisfactorily recovering all of the valuable componentcontained in lthe solution being treated.

In general, one of the advantages obtainable by the use of the presentinvention is to permit the obtaining of satisf-actory separation byusing lower centrifuging speeds. This is illustrated by the ability, bythe use of the present invention, to reduce the centrifugation speed ofaround 1700 G heretofore used in processes of the class described toabout 420 G and still obtain satisfactory separation.

While in a number of the examples the preferred oper- `ation has been toincorporate the agents after the formi-ation of the precipitate, theinvention is not limited in this respect. It is, however, generallypreferred to employ La+3 strike and follow this operation by theaddition of the agent. When using Aresklene, however, it has been notedthat maximum improvement is usually obtainedrby an HF strike in thepresence of the agent.

The use of agents in accordance with the present invention in processesfor recovering the Valuable product, Pu, apparently does not adverselyaffect existing procedures to which the invention may be applied. Thatis, the addition of the agents does not strip the Pu from lanthanumiluoride carrier precipitates, and apparently does not inhibit thecarrying of the Pu under process conditions. In instances where smallquantities of the agents may be carried through the subsequent steps ofthe process by the carrier precipitate as, for example, through themetathesis into the solution of metathesized product, this residuumapparently does not interfere with the oxidation of Pu and has noyadverse effect upon subsequent concentration cycles which may beapplied for concentrating or segregating Pu.

While my invention has been described as employed in preparing thefluoride type of precipitate, illustrated by lanthanum fluoride, sincethis constitutes the preferred embodiment as well as a type ofprecipitate frequently encountered in plant processes, my invention isnot limited thereto. Similar procedure may be applied in the formationof other precipitates exemplified by the formation of potassiumplutonium fluoride and plutonium peroxide precipitates or to BiPO4,CeF3, or other carrier precipitates containing Pu. In certain otherinstances precipitates which do not occulate or otherwise presentdifficulties of formation and separation may be improved by theapplication of the principles of my invention; for example, radioactivefission elements may be more completely separated with a BiPO4by-p-roduct precipitate when a surface active agent is used, or theagents may also be used to flocculate LaFa by-product precipitates.

The process may be applied to solutions containing Pu from traceramounts to several hundred milligrams per liter. The concentration ofLai3 ion may be from about 50 to 300 mg. per liter, added in severaladditions if desired. The concentration of HF may be within the range ofabout 0.2 to 2 N. While HF has been referred to as .the source offluoride ions, other reagents such as NaF, KF, and the like may be used.Such details are described in other copending applications and form nopart of the present invention excepting that in the present invention ithas been possible in many instances to use lower concentrations andobtain satisfactory results. However, my invention is not limited inthese respects as the concentrations of the reagents suggested laremerely guides to preferred practice. Likewise, metathesis refers to an.operation customarily Yemployed in processes of the pres ent type andinvolves the use of alkali metal hydroxides and/or carbonates in aprocess of converting uoride precipitates to .acid solutions thereof.Since such processes are described in detail in other applications,description herein is unnecessary.

It is to be understood' that all matter contained in the abovedescription and examples shall be interpreted as illustrative and not'limitative of the scope of this invention, and it is intended to claimthe present invention as broadly as possible in view of the prior art.

I claim:

l. In a process for the separation of plutonium from a solutioncontaining la compound of plutonium and compounds of other elements, inwhich an insoluble precipitate is form-ed in said solution and theprecipitate together with its associated plutonium is thereafterseparated from the supernatant solution, the improvement which comprisessubjecting said precipitate to the action of dibutyl-phenylphenol`sodium sulfonate prior to separating said precipitate from saidsupernatant solution.

2. In a process lfor the separation of plutonium from a solutioncontaining a compound of plutonium and cornpounds of other elements, inwhich 4an insoluble precipitate is formed in said solution and theprecipitate together with its associated plutonium is thereafterseparated from the .supernatant solution, the improvement whichcomprises forming said precipitate in the presence ofdibutyl-phenylphenol sodium sulfonate.

v3. In a process in which lanthanum fluoride is precipitated in anlaqueous solution and thereafter separated from the supernatantsolution, the improvement which comprises effecting said precipitationin the presence of `dibutyl-phenylphenol sodium sulfonate.

4. In a process in which bismuth phosphate is precipitated in an aqueoussolution and thereafter separated from the supernatant solution, theimprovement which comprises etfecting said precipitation in the presenceof dibutyl-phenylphenol sodium sulfonate.

References Cited in the tile of this patent UNITED STATES PATENTS1,697,543 Seidler Ian. l, 1929 1,792,863 Peet l Feb. 17, 1931 2,099,079Rumscheidt et al. Nov. 16, 1937 2,408,059 -Gareld et al. Sept. 24, 17946OTHER REFERENCES AEC Report No. CN-1409, semimonthly report for periodending March 31, 1944p-age 7, declassiiied March 19, 1957, 11 pages.

1. IN A PROCESS FOR THE SEPARATION OF PLUTONIUM FROM A SOLUTION CONTAINING A COMPOUND OF PLUTONIUM AND COMPOUNDS OF OTHER ELEMENTS, IN WHICH AN INSOLUBLE PRECIPITATE IS FORMED IN SAID SOLUTION AND THE PRECIPITATE TOGETHER WITH ITS ASSOCIATED PLUTONIUM IS THEREAFTER SEPARATED FROM THE SUPERNATANT SOLUTION, THE IMPROVEMENT WHICH COMPRISES SUBJECTING SAID PRECIPITATE TO THE ACTION OF DIBUTYL-PHENYLPHENOL SODIUM SULFONATE PRIOR TO SEPARATING SAID PRECIPITATE FROM SAID SUPERNATANT SOLUTION.
 3. IN A PROCESS IN WHICH LANTHANUM FLUORIDE IS PRECIPITATED IN AN AQUEOUS SOLUTION AND THEREAFTER SEPARATED FROM THE SUPERNATANT SOLUTION, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID PRECIPITATION IN THE PRESENCE OF DIBUTYL-PHENYLPHENOL SODIUM SULFONATE.
 4. IN A PROCESS IN WHICH BISMUTH PHOSPHATE IS PRECIPITATED IN AN AQUEOUS SOLUTION AND THEREAFTER SEPARATED FROM THE SUPERNATANT SOLUTION, THE IMPROVEMENT WHICH COMPRISES EFFECTING SAID PRECIPITATION IN THE PRESENCE OF DIBUTYL-PHENYLPHENOL SODIUM SULFONATE. 